JPS6051681B2 - light reflector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film type light reflector comprising a dielectric layer and a metal layer.

For this type of thin film light reflector, for example, a dielectric layer with a relatively high refractive index is laminated on a dielectric substrate with a relatively low refractive index, and portions of the dielectric layer are layered to form a desired light reflector. A structure that is removed by etching is known.

However, in the light reflector created in this way, the etched side surface, that is, the lateral boundary surface, has boundary irregularities on the order of the wavelength of light, so this poor surface precision causes a large light scattering loss, making it difficult to improve the It was difficult to obtain things.

The present invention aims to alleviate these drawbacks, and includes a first dielectric layer having a relatively large refractive index formed on a dielectric substrate, and a layer laminated on the first dielectric layer. This is achieved by a structure in which a second dielectric layer with a relatively small refractive index and a metal layer with a desired pattern are laminated, and will be described in detail below with reference to the drawings.

Fig. 1 is a plan view showing one embodiment of the present invention, and Fig. 2 is a plan view showing an embodiment of the present invention.
A sectional view along the X and -Y directions in the figure, and FIG. 3 is the x in FIG. 1.

-Y. It is a sectional view along the direction. In Figures 1 and 2, 1 is a dielectric substrate with a relatively low refractive index, 2 is a first dielectric layer with a relatively high refractive index, and 3 is a second dielectric layer with a relatively low refractive index. The layers 4 are air, 5 is a metal layer, and 6 is an incident beam of light.

Coupling of the input and output light with the incident light beam 6 in the first dielectric layer 2 can take place via prism couplers 7a, 7b. Also, n,, n2, n3, n. , are the optical refractive indexes of the materials of the dielectric substrate 1, the first dielectric layer 2, the second dielectric layer 3, the air 4, and the metal layer 5, respectively.
In this embodiment, a dielectric substrate 1, a first dielectric layer 2, a second
The dielectric layer 3 and the metal layer 5 are sequentially made of SlO2.
Using a substrate, Al2O3 layer, SiO2 layer, and Al layer, Si
High frequency sputtering method (or C.V.D.
・Al2O3 layer 2 of several thousand amps or several μm is deposited using the same method (method or other method), and then a SiO2 layer 3 of several thousand amps is deposited using the same method. Alternatively, the film may be deposited by a photo-etching method after vapor deposition, etc.).

With this structure, the equivalent refractive index of the first dielectric layer 2 in contact with the metal layer 5 via the second dielectric layer 3, that is, the equivalent refractive index of the first dielectric layer 2 in the region A is approximately 1.6
04 and the first dielectric layer 2 in the B region in contact with the air 4
The equivalent refractive index of is approximately 1.636, and a refractive index difference occurs in the first dielectric layer 2 according to the pattern of the metal layer 5.

Due to this refractive index difference, a lateral boundary surface is generated in the dielectric layer 2, and if the incident angle of the incident light beam is set appropriately, the equivalent refraction shown by the broken line in FIGS. 2 and 3 can be achieved. It is reflected at the boundary of area A where the rate has decreased. In addition, this light reflector
Depending on the setting of the incident angle, it can also be used as a light splitter as shown in FIG. With the structure of this embodiment, it is easy to manufacture, the ohmic loss of the metal layer is small due to the effect of the second dielectric layer, and the light scattering loss at the lateral boundary surface, which is a light reflecting surface, is reduced. It is possible to obtain a light reflector with low cost and high efficiency.

Next, the reason why the optical transmission loss in the first dielectric layer 2 is reduced by providing the second dielectric layer 3 on the first dielectric layer 2 will be described.

The propagation constant β of light in the dielectric layer 2, the attenuation constant α of light. The relationship between the thickness T2 of the dielectric layer 2 and the thickness b of the dielectric layer 3 is as follows:
It is well known that b = 0 (for example, Applied
Optics Vol. 12 No. 5 A. (Reisinger)) The relational expression can be expressed as an extension of the following expression. Here, γ4 = 1, γ32 = 1, γ53 = 1 (for TE mode) (for TM mode), λo is the wavelength in vacuum, ε1, E・2, E
3, E4, and E5 are wavelengths λ.

The dielectric constant of each substance of the dielectric substrate 1, dielectric layer 2, dielectric layer 3, air 4, or metal layer 5, that is, the thickness of the thin film dielectric layer that becomes the optical transmission path, and b is the intermediate insulating layer. 3 thickness, N is the order of light, Nl, n2, n3, rl4, n5
are dielectric substrate 1, dielectric layer 2, dielectric layer 3 for λo
, the refractive index of the substance of the air 4 or the metal layer 5,
It is. The materials of the dielectric substrate 1, dielectric layer 2, dielectric layer 3, and metal layer 5 are each made of SlO. ,A]203,Si02
, A1 and the refractive index n1=1.48, n2=1.88,
n3=1.48, Akira=1.2-J7. The thickness of the dielectric layer 2 was 3000A, and the thickness of the dielectric layer 3 was 300A, using a He-Ne laser beam with a wavelength of 6328A (7).
0A, and when the lateral width of the removed portion of the metal layer 5 is 8.5 μm, the amount of attenuation for the TEO mode propagating light is 4d.
B/Arl is about 85 in the case where the dielectric layer 3 is not provided.
dB/c! This is a huge improvement compared to RL.

In addition to the prism coupler 7, coupling of input and output light with the incident beam 5 in the dielectric layer 2 can also be achieved by forming a diffraction grating on the surface of the dielectric layer 2 and interfering with the incident beam 6. .

Alternatively, an active layer such as a semiconductor laser may be embedded in the dielectric layer 2. Furthermore, as shown in FIG. 5, by placing metal layers 5a and 5b facing each other, an optical resonator can be constructed between them.

As explained above, according to the present invention, the scattering of light at the lateral boundary surface can be reduced and the loss of transmitted light can also be reduced, so it has advantages such as good reflection efficiency and easy manufacture.

[Brief explanation of drawings]

Fig. 1 is a plan view of a light reflector showing an embodiment of the present invention, Fig. 2 is a sectional view taken along the line X1-Y1 in Fig. 1, and Fig. 3 is a sectional view taken along the line X2-Y2 in Fig. 1. FIG. 4 is a plan view of a light splitter showing another embodiment of the present invention, and FIG. 5 is a plan view of an optical resonator showing another embodiment of the present invention. 1... Dielectric substrate, 2... First dielectric layer, 3... Second dielectric layer, 4... Air,
5... Metal layer, 6... Incident beam light, 7
・・・・・・Prism coupler.

Claims (1)

[Claims] 1. A first dielectric layer having a relatively high refractive index laminated on a dielectric base having a low refractive index, and the first dielectric layer having a relatively low refractive index and laminated on the first dielectric layer. a relatively thin second dielectric layer that reduces loss of propagating light guided through a specific portion of the first dielectric layer, and a metal layer laminated on the second dielectric layer; A light reflector in which the metal layer is formed in a band shape perpendicular to the traveling direction of light or at a certain angle with respect to an optical transmission path formed in the light transmission line.